1,1-Ethanediol, dehydration

Ethanediol (ethylene glycol) [5g] Commercial products are pure enough for most purposes. In order to remove water of 2000 ppm, the ethanediol is dehydrated with sodium sulfate anhydride and distilled twice at reduced pressure in a dry nitrogen atmosphere in order to avoid oxidation to aldehyde. 

Polymers usually are prepared by two different types of polymerization reactions — addition and condensation. In addition polymerization all of the atoms of the monomer molecules become part of the polymer in condensation polymerization some of the atoms of the monomer are split off in the reaction as water, alcohol, ammonia, or carbon dioxide, and so on. Some polymers can be formed either by addition or condensation reactions. An example is polyethylene glycol, which, in principle, can form either by dehydration of 1,2-ethanediol (ethylene glycol), which is condensation, or by addition polymerization of oxacyclopropane (ethylene oxide) 1... 

Ethanediol. See Ethylene glycol Ethanoic acid. See Acetic acid Ethanol, 128, 130, 580-581 acidity of, 135, 740-741 and benzaldehyde, acetal from, 669 biological oxidation of, 600—602 chemical shifts, 606 conversion to diethyl ether, 592 dehydration of, 182 dipole moment of, 130, 863 by fermentation, 580-581 hydrogen bonding in, 130-131 industrial preparation of, 223, 581 physical properties of, 130, 132-133, 580 reduction of aryl diazonium salts by, 894, 907... 

Reaction with Di- and Polyols. Although intermolecular dehydration between two molecules of alcohols to afford acyclic ethers usually does not occur with the DEAD-TPP system, intramolecular cyclization of diols to produce three to seven-membered ethers is a common and high yielding reaction. Contrary to an early report, 1,3-propanediol does not form oxetane. Oxetanes can be formed, however, using the trimethyl phosphite modification of the Mitsunobu reaction. The reaction of (5)-1,2-propanediol and ( )-l,4-pentanediol with DEAD and TPP affords the corresponding cyclic ethers with 80-87% retention of stereochemistry at the chiral carbon, while (5)-phenyl-1,2-ethanediol affords racemic styrene oxide. In contrast to the reaction of the same 1,2-diols with benzoic acid (eq 4), oxyphos-phonium salts (25a) and (25b) have been postulated as key intermediates in the present reaction (eq 20). ... 

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